1. Field of Invention
The present invention relates generally to an apparatus for generating a seismic signal and method for utilizing such apparatus in conducting seismic exploration of subterranean strata, and more particularly, to such an apparatus and method wherein a propellant is employed to generate repeatable, reliable seismic sources from a downhole location in a subterranean well bore.
2. Description of Related Art
Seismic data which is recorded by recording devices placed in an array at the surface of the earth or on the sea floor is increasingly used to evaluate and map subsurface structures for the purpose of exploring for and exploiting oil, gas and/or mineral reserves. Impact devices, such as vibratory sources, gas guns, air guns, and weight drops, have conventionally been employed at the earth's surface as a seismic source to generate shear and compressional waves in subterranean strata. Often, it is desirable to locate a seismic source at a downhole location in proximity to the particular subterranean strata(s) of interest. In view of this, a need exists for a seismic source which is located in a subterranean bore hole which is reliable and which generates repeatable, broad bandwidth compressional and/or shear waves while imparting minimal damage to the bore hole.
Thus, it is an object of the present invention to provide an apparatus for generating a seismic signal and method for utilizing such apparatus in conducting seismic exploration of subterranean strata which generates repeatable, reliable seismic sources from a downhole location in a subterranean well bore.
It is also object of the present invention to provide an apparatus which utilizes solid propellant for generating a seismic signal in a subterranean bore hole.
It is another object of the present invention to provide an apparatus for generating seismic signals utilizing propellant wherein the dimensions of the solid propellant may be varied to produce compressional and/or shear waves of varying amplitude and/or frequency.
It is still another object of the present invention to use downhole pressure gauges to relate pressure data to seismic data and as a result vary the propellant dimensions of the seismic source apparatus to obtain the desired compressional and/or shear waves.
It is a further object of the present invention to provide an apparatus for generating a seismic signal which may be employed in a subterranean bore hole which is either cased or open hole.
It is a still further object of the present invention to use computer modeling software to create the desired seismic energy source by selecting the geometric configuration of the propellant before actually conducting work in real well bores and to use the field data from fast recording pressure, acceleration, and strain gauges to validate the accuracy of the computer modeling estimates.